Receiving device for light signals



May 30, 1933. I w BISCHOFF 1,911,986

RECEIVING DEVICE FOR LIGHT SIGNALS Filed 001:. 15, 1931 Patented May 30, 1933 UNITED STATES PATENT OFFICE WERNER BISCHOFF, OF JENA, GERMANY, ASSIGNOR 'IO FIRM CARL ZEISS,

GERMANY OF JENA,

RECEIVING DEVICE FQR LIGHT SIGNALS Application filed Octane: 3.5, 1931, Serial No. 569,1CO, and in Germany October 21,1930.

The present invention relates to a receiving device for light signals, which is provided with light-sensitive cells and is ap plied for instance in optical train control systems. When using this device it is generally not possible to have the light-sensitive cells struck only by the light for transmission of signals and not also by other light, for instance daylight, which is not to be permitted to produce any effect on the receiving device. This disadvantage is obviated by equipping the device, in addition to the cells for receiving the light signals, which are hereinafter termed effective cells, with cells for compensating the effects produced by daylight and similar illuminations. A group of effective cells and an equal group of compensating cells are connected in series a in a circuit and the potentials for operating the control circuits are taken from the ends of one of these groups. The desired effect is always obtained when the cells are exposed to light in the predetermined manner, that is to say when with existing detrimental light both the effective and the compensating cells are simultaneously exposed to this detrimental light, and, when any detrimental. light does not exist, only the effective cells are struck by the light for signal transmission. It has proved however that not only these predetermined but also other exposures have to be taken into consideration, for instance exposures caused by mischievously directing strong light to all effective and only to part of the compensating cells by means of a pocket mirror. The known device cannot provide any sufficient compensation to meet this case which may be rather seldom but is nevertheless possible. A criminal interference is to be feared especially with the optical end signals of trains, in the case of which the receiving device and a light source for influencing the same are close together and easily accessible near the track.

The object of the present invention is to give the known device a compensation which is by far more efficient and can deal with any unfavorable illumination. This can be achieved by substituting for the usual equal,

' cells of the effective group in series and the cells of the compensating group in parallel. This compensating group may as well consist of one single cell.- As hitherto, care is to be taken that the sensitivity of all cells is the same, in other words, the ratio of the resistance of a cell in a definite illumination to the resistance of this cell in the dark must be always equal. It has been proved that the connection according to the invention makes the difference between the effect due to the required kind of illumination and that due to any possible undesired kind of illumination greater than hitherto, the consequence being that it is easily possible to so adjust a relay influenced by the light-sensitive cells that it does not react upon undesired illuminations, whereby the casein which all effective cells, that is to say these cells alone, are mischievously illuminated is of course left out of account.

With a view to also prevent any such mischievous illumination as far as possible, the effective and compensating cells are mixed in a suitable manner. It is convenient to provide two effective and two compensating cells and to arrange these cells in a circle in such a manner that the two effective as well as the two compensating cells are diametrically opposite each other. The arrangement permits both effective cells to be illuminated. in the predetermined man ner for instance by means of a suitable triple mirror, any criminal illumination of the two effective cells thus requiring a mirror of definite form which is not easy to be had at once.

The cells according to the invention are suitably used together with a cathode ray relay and leads are branched from the ends of one of the cell groups to the grid of one of the electrodes of an amplifier valve.

The accompanying drawing illustrates the object of the invention in a device hav ing two effective and two compensating cells. Figure 1 shows the connection of the cells, no regard being had to their spatial arrangement. Figure 2 is a complete conticn diagram of tour cells arranged in a circle and Connected to an amplifier valve.

A cording to the diagram represented by fare I a group A of ellective cells and a group B of compensating cells are connected c ies to t e circuit of a battery 0. The group it cor of two cells a and a which are connected in series, and the group I3 con s of two cells If and connected e1. From the ends of the group A branch to a relay d which is to become effective as soon as the two cells a and c ated by the signal light. The re- (Z must not act when all cells are illumiby day ght or when some of the cells, or :t'or instance the cells a 6 and 5 are TB'POSdtl to an illumination stronger than at reflected onto the cell a I, the constructional example according to Figure 2 the cells a a b and b are arranged in a circle C, in the corners of a suuare the cells a and a lying on the one curl, and the cells 6 and b on the v et er. The relay (Z an amplifier valve l 'ing a cathods d a grid (Z and an anode (1*. The group of the effective cells is connected direct to the cathode (K and by means oi a condenser e to the grid (Z of the valve (Z. Between the grid and the cathode are provided a tension battery f and a grid res stance 7. I claim: 1. A device for receiving hght signals,

coinpr a source of current, a relay, a group t-sensitive cells connected in series and ving the purpose of energizing the relay, anoth r group of light-sensitive cells connected in parallel, the cells of this other group having the same sensitivity as the cells ot the first said group and serving the purpose of compensating the effect of detrimental light. the two groups being connectcd in series in a circuit containing the said source of current, and the relay being connected to the two ends of one of the two groups.

device for receiving light signals, a source of current, a relay, one

flit-sensitive cells connected in sethe ay, another pair of light-sensitive its connected in parallel, the cells of this other group having the same sensitivity as the cells ot the first said group and serving ihe purpose of compensating the effectoi detrimental light, the tour cells being arranged in a circle, the two cells of the first said pair lying on one diameter and the two 's of the other pair lying on another meter of this circle, the first said pair being connected in series to the other pair in a circuit containing the said source of current, and the relay being connected to the two ends of one of the two pairs.

comprising a source of current, a relay, one pair of light-sensitive cells connected in series and serving the purpose of energizing the relay, another pair of light-sensitive cells connected in parallel, the cells of this other group having the same sensitivity as the cells of the first said group and serving the purpose of con'ipensating the effect of detrimental light, the four cells being arranged in the corners of a square, the two cells of the first said pair lying on the one diagonal and the two cells of the other pair lying on the other diagonal of the said square, the first said pair being connected in series to the other pair in acircuit containing the said source of current, and the relay being connected to the two ends of one of the two pairs.

YVERNER BISCHOFF. 

